Title page for etd-0905102-181359


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URN etd-0905102-181359
Author Tzong-En Wu
Author's Email Address No Public.
Statistics This thesis had been viewed 5343 times. Download 1465 times.
Department Marine Geology and chemistry
Year 2001
Semester 2
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title Radioactive disequilibrium Between Pb-210 and Po-210 in Water Columns of the Northern South China Sea
Date of Defense 2002-07-29
Page Count 63
Keyword
  • SPM
  • Northern South China Sea
  • Pb-210
  • Po-210
  • Abstract The purposes of this study are to understand the variations of the particulate and dissolved Pb-210 and Po-210 in profiles in the South China Sea and to estimate the residence time of these nuclides through their extent of radioactive disequilibrium. The profiles of Pb-210 and Po-210 in particulate and dissolved phases were measured at four stations in the northern South China Sea (station B, C, D and F) and three in the Bashi Channel (stations W2, W3 and W5) from four Ocean Researcher I cruises (ORI-575, ORI-580, ORI-588 and ORI-606). At Station C two profiles were taken, one before and the other after a typhoon to see its effect, if any, during the ORI-588 cruise. As the associated Ra-226 profiles were not measured their relations to Pb-210 profiles are not available for discussion in this thesis.
    The mean suspended particulate matter (SPM) concentration for each station is about 0.2 mg/kg with small deviations. Activities of Pb-210 and Po-210 in the northern South China Sea were all higher than those in the sea off NE Taiwan easured during the KEEP program. The dissolved Pb-210 profiles generally display a maximum around 15 to 25 dpm/100kg in the surface layer due to atmospheric input, and a minimum of about 5 to 15 dpm/100kg from 300 to 1000 m. The activities below 1000 m vary only slightly with a deep maximum as high as 20 dpm/100kg around 2000 to 3000 m, as seen at Station C. The particulate Pb-210 is around 3 to 5 dpm/100kg with small variation for the entire water column. The dissolved Po-210 profiles are somewhat similar to the dissolved Pb-210 profiles, but lower by about 5 to 10 dpm/100kg in activity. The mean residence time is about 0.76 year for total Po-210 in the entire water column, and 0.35 to 2.13 years for total Pb-210 in the mixed layer. At each station, Po-210 is deficient relative to Pb-210 in either the particulate or dissolved phase. The mean total
    Po-210/Pb-210 activity ratio is about 0.58, indicating that Po-210 is more effectively scavenged. It is imperative to understand the fate and pathway of the missing Po-210. Judging from its biophilic nature, Po-210 may have been absorbed or consumed by biomass and enriched in
    various tropic levels in the food chain, in addition to being scavenged and removed by sinking particles.
    Advisory Committee
  • none - chair
  • none - co-chair
  • Yu-chia Chung - advisor
  • Files
  • etd-0905102-181359.pdf
  • indicate access worldwide
    Date of Submission 2002-09-05

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